I know it is not real ale, but there is a real cider festival at the East Anglian Railway Museum, Chappel & Wakes Colne nr Colchester (Same location as the Chappel Beer Festival) this weekend, Thur eve to Sunday Lunch time. About 30 ciders and 2 Real Ales on offer.
Easy rail access, as the "One" Railway Chappel & Wakes Colne station is immediately alongside (30 second stagger away)